Our previous studies have characterized a nocturnal hemodynamic pattern in a variety of mammals, including man, comprised of a decline in cardiac output and an elevation in total peripheral resistance. In patients with heart disease, this pattern could exacerbate the incidence of morbid events which are known to occur in the morning. This project is designed to evaluate overnight cardiovascular patterns in selected patient groups, and to test the effectiveness of interventions designed to ameliorate specific adverse effects. Findings to date indicate that postural change (30 min standing after reclined position) results in a substantial elevation of blood viscosity and hematocrit, but an eight-oz drink does little to attenuate posture-dependent rheologic responses.